The present invention relates to an ink jet printer and more particularly to a print head for an ink jet printer including an ink passage whose wall is treated to obviate defective ink ejection.
It is a common practice with an ink jet printer to provide its ink passage with a hydrophilic wall for promoting the flow of ink and bubbles contained in the ink. Japanese Patent Laid-Open Publication No. 7-276629, for example, proposes to implement hydrophilicity by causing ozone with a preselected concentration to flow through the ink passage. Japanese Patent Laid-Open Publication No. 7-290714 teaches that an aqueous solution of an organic emulsion is circulated through the ink passage and then dried.
The above hydrophilicity of the wall of the ink passage is directed toward high wettability of the ink passage, i.e., smooth flow of the ink and bubbles contained therein. This kind of scheme allows a minimum of bubbles to remain in the ink passage and obstruct ink ejection when the ink passage is filled with the ink.
However, after the ink passage has been filled with the ink, a small amount of bubbles sometimes intermittently flow from, e.g., a cartridge upstream of the ink passage into the passage while the printer is in operation. Such bubbles would reach nozzles and render ink ejection from the nozzles defective. Moreover, should the bubbles gather on a filter and form a film thereon, they would increase resistance to the flow of the ink and obstruct ink feed into the head, also resulting in defective ink ejection.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 4-173345, 5-345419, and 6-40040.